Earpieces for oximeters



April 30, 1957 R. H. TAPLIN ETAL EARPIEcEs FOR oxIMETERs 2 Sheets-Sheetl Filed Jan. l5, 1956 April 30, 1957 R. H. TAPLIN ETAL 2,790,438

EARPIECES FOR OXIMETERS Filed Jan. 13, 1956 2 Sheets-Sheet 2 which,unlike the rubber capsules previously used does not change its colourwith age.

The invention will now be described with the assistance of theaccompanying drawings, wherein a preferred embodiment is shown. It willbe realized that various changes could be made in the embodiment shownand described and other apparently different embodiments of theinvention could be constructed without departing from the scope thereof.Accordingly it is intended that :all matter shown in the accompanyingdrawings or described herein shall be interpreted as illustrative andnot in a limiting sense.

In the drawings wherein like parts are denoted by identical referencenumerals,

, Figure l shows an oblique threeuarters view of a preferred embodimentof the invention;

Figure 2 shows a side elevation View of the device illustrated in Figurel;

Figure 3 shows a cross-sectional view of the device illustrated inFigures l and 2 as it would be used in association with the pinna of theear;

' Figure 4 shows a fragmentary cross-sectional view indicating thestructure 4of the inilatable capsule;

IFigure shows a cross-sectional view `taken as at 5 5 in Figure 2;

Figure 6 shows an oblique three-quarters partly eX- ploded view of thedevice; and

Figure 7 shows a circuit diagram illustrating the function of the devicedescribed herein.

' Referring to the accompanying drawings wherein the same referencenumerals denote like parts in all figures, the earpiece device will beseen to have a bifurcated or clamp-shaped structure adapted to surroundthe pinna of the ear. For convenient reference the earpiece may bedescribed -as consisting of a light-emitting portion, which iscylindrical in shape and a light-receiving portion of box-likeappearance connected by a bracket denoted by 2. The pinna of the ear isdenoted by 1.

The light adapted to be transmitted through the pinna 1 'is supplied byany convenient source, such as a small incandescent lamp shown at 3.Lamp 3 preferably consumes approximately one watt, which, in addition tosupplying the necessary light, will provide suilicient heat to dilatethe blood vessels of the pinna 1. It` is contemplated that alternatingcurrent of a frequency of, for example 30 cycles per second will besupplied to lamp 3, the reason for which will be apparent below. Lamp 3is mounted in a conventional socket, shown at 4, and socket 4- issuitably held in a tubular lamp holder denoted by 5.

Lamp holder 5 is preferably provided with a pair of flanges denoted by 6and 7, flange 7 being at the end of ltubular member 5 and of slightlylarger diameter than flange 6. The purpose of iianges 6 and 7 is toeffect suitable mounting on bracket 2 and to this end bracket 2 isprovided with a ring denoted by 8 of such internal diameter that ange 6slides easily wihtin ring 8 but flange 7 is unable to enter the saidring. A set-screw denoted by 9 is threadably mounted in a suitableopening in the part of bracket 2 where the latter is formed into ring S.The power supply wires for lamp 3, denoted by 10 and 11, pass out oflamp holder 5 -through one or more suitable openings.

Extending from lamp holder 5 is a telescopic tubular member denoted by12 having an internal diameter such that it is able to receive lampholder 5 therewithin, and is able to slide freely over the said lampholder. It is contemplated that the ends of tubular member 12 oppositelamp holder 5 will be pressed toward the pinna 1 in a manner to bedescribed below.

A helical spring denoted by 13 is provided inside tubular member 12, andit is preferable if spring 13 is of such size that it touches theinternal walls of tubular member 12 without sticking or binding. At theend of tubular member 12 opposite lamp holder 5 is a transparent windowdenoted by 14.V A slidable collar shown` at 15 is also provided of suchsize that it moves easily along the inner wall of tubular member 12, andit is contemplated that spring 13 will urge Window 14- and collar 15apart thereby tending to telescopically extend tubular member 12 awayfrom lamp holder 5.

Attached to collar 1S is a threaded shaft denoted by 16 and shaft 16passes loosely through an unthreaded opening in bracket 2, denoted by17. A clamping nut denoted by 18, suitably threaded to engage shaft 15is provided, and it will be apparent that when clamping nut 1S istightened, tubular member 12 is locked between collar 15 and bracket 2.A slot, denoted by 19 is provided in tubular member 12 so that whenclamping nut 18 is loose, tubular member 12 may be telescopically slidon lamp holder 5, and will be urged away from the said lamp holder; andalternatively, the tightening of clamping nut 18 will lock tubularmember 12 in whatever position it then happens to be in relation to lampholder 5.

The window 14 at the end of tubular member 12 has already been referredto. For reasons which will be apparent below, window 14 should be somounted in tubular member 12 that an air-tight seal is produced. Inorder to provide appropriate pressure on pinna 1, it is contemplatedthat an inatable capsule will be provided by stretching a resilientmembrane over window 14 and incorporating means for supplying air underpressure to the space between the window 14 and such membrane. Themembrane, denoted by 20 is preferably made of polyvinyl acetate plasticfilm which does not change its colour with age. Membrane 2i) isstretched over the end of tubular member 15 and secured by a fasteningring denoted by 21, which may be, for example, several strands of threadwound therearound. An air tube denoted by 22 communicates with the spacebetween window 14 and membrane 20, and a iiexible tube, denoted by 23 isused to apply air under pressure to tube 22.

It will be apparent that the device disclosed above is convenient forapplying the proper pressure to the pinna 1. The telescopic relationshipof tubular member 12 and lamp holder S, and the action of spring 13provides a simple manner of engaging vpinnae of a wide range of sizes.When such engagement is made, clamping nut 18 may be tightened to holdtubular member 12 in place, and appropriate air pressure can then beapplied to tube 23 to compress the pinna to the required degree and torelease such pressure when desired.

Referring now to the light-receiving portion of the device, in contactwith which ination of membrane 20 compresses pinna 1, the saidlight-receiving portion consists of two housing members denoted by 24and 25 and various components contained therein, kto be described below.Housing member 24 is integraly with bracket 2 and housing member 25 isattached to housing member '24 by means of capscrews denoted by 26.

Held within housing members 24 and 25 is a block of transparent materialdenoted by 27, preferably of the particular shape shown. Block 27 ispreferably of an acrylic resin with suitable optical properties such asLucite which provides a significantlight-pipe effect common to suchmaterials. The light-pipe elect is produced by the combination oftransparency and a highly reective surface and accordingly various othermaterials having similar characteristics could of course be used.

It is intended that the light transmitted through the pinna' will begathered by block 27 and transmitted through a length at least threetimes that of the aperture diameter where the light enters block 27,with little light loss and absence of image formation.

Block 27 has a forward polished face denoted by 27a forming thelight-receiving aperture adapted to touch the pinna 1. Housing member 24is so constructed that forward portion 27a lies flush with the surfaceof housing member 24facing tubular member 12. Block 27 also hasadiagonal face denoted by 27b,the surface of n which is also polished.The remainder of block 27 deiined` by surfacesdenoted by 27d and 27e'isa simple rectangular prism highly polished so Vas to reflect any lightfalling upon its inner `surface. The end of block 27 opposite face 27ais denoted by 27c, and attached'to face 27e is a filter block, denotedby 28 to be described below. Obviously, all the surfaces of block 27have ito be fiat as opposed to rounded, otherwise thereY would be atendency to focussing, with bright andY dull gradations of lightintensity.

The manner in which the light is transmitted from lamp 3 will beapparent from the foregoing description, but for greater certainty willnow be `reiterated. Light from lamp 3 passes through4 window 14,membrane 20 and thence through pinna 1 where it falls upon the surface27a of block 27. 'It will be apparent that the pinna 1 being translucentbut not transparent will transmit light therethrough in such a mannerthat the light passes out of the pinna 1 through a solid angle of 180.Accordingly the light reaching surface 27a is passing in every directionand is necessarily scattered. A large portion of the light sotransmitted falls upon surface 27b, and as a result of thecharacteristics of the surface 27b previously referred to, such light isfurther scattered. The light not falling on surface 27b strikes thesurface 27d over that portion of its surface which is adjacent surface27a and by virtue of the light scattering characeristics of the block 27is reflected downward to surface 27e and thence to filter block 28. Inthe result, the light reaching filter block 28 is almost completelyscattered and entirely homogeneous and forms no image.

The filter block 28 attached to block 27 will now be described. As seenin Figure 7 the filter block consists of four filter components denotedby reference numerals 28a, 28b, 28C and 28d. Integral with the saidfilter components are photoelectric cells denoted by 29a, 29b, 29e and29d, respectively.

The filter components 28a and 28d are so arranged as to provide maximumsensitivity of photoelectric cells 29a and 29d at 650 mp and filtercomponents 28b and 28e will provide maximum sensitivity of photoelectriccells 29h and 29e at 800 mp.. It will be appreciated that it is notnecessary that the sensitivity characteristics be in the exactarrangement described, and there are several obvious juxtapositions.Photoelectric cells 29a and 29d are connected to outlet lead 30 andphotoelectric cells 29b and 29e are connected to outlet lead 31. Leads30 and 31 are connected to amplifier means to be described below wherethe light transmission characteristics are interpreted in terms ofdegree of blood oxygenation.

Leads 30 and 31 pass through a cable denoted by 33 which connects theearpiece to the amplifiers. Since the leads 30 and 31 carry very weakcurrents, it is preferable that they be shielded. Lines and 11 alreadyreferred to also pass through cable 33. Line 10 passes through anopening in housing 24, denoted by 32 and thence to lamp 3. Line 11 alsopasses through opening 32 and to the other side of lamp 3, and line 11is connected to the body of housing 24 near where it enters cable 33.A-t the end of cable 33 opposite the earpiece, line 11 is suitablygrounded. The current supply for lamp 3 is shown at 34 and furnishes anoscillating current of the order of cycles per second.

Lead 30 is connected to an amplifier denoted by 35 and lead 31 isconnected to a second amplifier denoted by 36. These two amplifiers arequite conventional and are similar except for one feature to bedescribed below.

The output of amplifier 35 is applied to a rectifier shown at 37 whichis in turn connected to a vacuum-tube voltmeter the principal componentsof which are triode 38 and meter 39. A bias control shown at 40, and anassociated rectifier shown at 41 are also provided.

Amplifier 36 is similarly connected to a rectifier shown at 42, which isin turn connected to vacum-tube voltmeter elements consisting of triode43 and meter 44. A

YIt will be apparent that there are two principal variables hereinvolved, namely the thickness of the -pinna through which light istransmitted, and the attenuation of the light because of the degree ofoxygen saturation. It is contemplated that the amplifier 36 will providethe means of measurement ofthe degree of oxygen saturation, and

amplifier 35 will provide a correction for the vthicknessl of the pinnaobserved. Accordingly, amplifier 36'- will sense the amplitude of wavesresulting from 'lighttransmitted of the order of 60 mp. (red) andampliiierfSS will sense the amplitude of waves resulting from lighttransmitted of the order of 800 my. (infra red). Since the latter arenot significantly affected by the degree of oxygen saturation, it isconvenient -to use amplifier 35 to provide the correction for the pinnathickness.

A description of the operation of the device will illustrate the methodof calibration as well as the other operational features. The pinna isfirst placed in the proper position as shown in Figure 3 and themembrane 20 is inflated so as to press most of the blood out of thepinna. Lamp 3 will then be emitting light as well as heat, and this heatwill assist in dilating the blood vessels of the pinna, so as to assistin providing light transmission therethrough. The light passes throughthe pinna 1 rela-tively easily. Since the light is produced by anoscillating current of the order of 30 cycles per second, there will beproduced at the photoelectric cells modulated waves of the samefrequency, and these waves will be passed to amplifiers 35 and 36. Bothmeters 39 and 44 will normally show initial readings and bias controls40 and 45 are then adjusted so that both meters 39 and 44 read zero.

The pressure on membrane 20 is then released and a definite reading willthen be shown on meters 39 and 44. There is a-relationship between thereadings of meters 39 and 44, such that a plot of V(where R47 is theresistance of shunt 47, R44 is the resistance of meter 44 and Ias is thecurrent read at meter 39) is a straight line. That is to say, theamplifier 36 may be corrected by adjustment of shunt 47 in accordancewith the reading of meter 39 to allow meter 44 `to give an indicationwhich is independent of the thickness of pinna 1. Meter 44, by suitablecalibration with the assistance of .known samples of arterial blood, the`oxygen saturation of which is determined gasometrically, can indicatepercentage saturation directly.

After shunt 47 has been adjusted as above, meter 44 will show a changedreading, and this new reading by virtue of the calibration referred towill indicate percent oxygen saturation. It may be mentioned that thedevice may be continued in use for a considerable period after it hasonce been put in operation as described, and it is only necessary tochange the setting of shunt 47 in accordance with the reading of meter39," if necessary, to restore correct conditions, and the condition ofthe blood of the subject wearing the device described will becontinuously indicated on meter 44.

It will be seen that the device described herein has numerousadvantages; it is simple and rugged in construction, simple to apply andcan be used Without extensive training on the part of the operator.

What is claimed is:

1. An oximeter earpiece capable of being used in as sociation with thehuman ear, comprising a source of light adapted to be placed on one sideof a portion of the ear,

averties a -light scattering means adapted to be placed on the oppositeside ofthe said portion of the ear, said light scattering meansconsisting of a polished transparent block having a at surface facingsaid source of light, an angular face making an acute angle with saidHat surface and a rectangular prismatic section oneend of which isformed by said angular face, a bifurcated frame member attached to saidsource of light and to said light scattering means and photoelectriclight-receiving means attached to said frame member on the same sidethereof as said light scat tering means.

2. A device according to claim l, wherein said photoelectric lightreceiving means consists of a plurality of photoelectric cells adjacentthe end of said light-scattering means opposite said angular face, andhaving lter means interposed between said photoelectric cells and saidlight scattering means.

Y 3. A device according to claim 1, Ywherein said photoelectric lightreceiving means consists of a plurality of photoelectric cells one halfof which have maximum sen sitivity at the region of 650 ma and the otherhalf of which have maximum sensitivity at the region of 850 mu, saidcells which have maximum sensitivity at the region of 650 my. beingintel-spaced with said cells having maximum sensitivity at the region of850 mp, and having in addition, lter means interposed between saidphotoelectric cells and said light scattering means.

References Cited in the le of this patent UNITED STATES PATENTS2,754,819 Kirschbaum July 17, 1956

